Gibraltar's Macaques Adapt to Tourist Diets by Eating Soil

Researchers have documented a notable behavior among the Barbary macaques of Gibraltar, where these monkeys have begun to consume soil, a practice known as geophagy. This behavior appears to be a response to the high intake of junk food from tourists, which includes items such as chocolate, crisps, and ice cream. The study, published in *Scientific Reports*, indicates that macaques with more frequent contact with tourists are more likely to engage in soil consumption, particularly during peak tourist seasons.

The GuardianMonkeys learn to self-medicate with soil to help them digest junk foodReuters

The Barbary macaques, numbering around 230 and divided into eight groups, are the only free-ranging monkey population in Europe. Local authorities provide them with fruits, vegetables, and seeds, but tourists often feed them high-calorie snacks that disrupt their natural diet. Dr. Sylvain Lemoine, a biological anthropologist at the University of Cambridge and lead author of the study, suggests that the consumption of these human foods can lead to digestive issues due to their high sugar, fat, and dairy content. The soil-eating behavior may help mitigate these effects by providing beneficial bacteria and minerals that are absent from the junk food.

The Guardian

The researchers observed that the macaques seem to learn the habit of eating soil from one another, with different troops favoring specific types of soil. For instance, while most macaques prefer the red clay found across Gibraltar, the Ape’s Den troop opts for tar-clogged soil from asphalt roads. This social learning aspect highlights how the macaques are adapting to their changing environment, similar to cultural behaviors seen in other primate species.

The Guardian

Despite the intriguing adaptation, experts caution against the continued feeding of junk food to the macaques. Dr. Paula Pebsworth, a primatologist at the University of Texas at San Antonio, argues that while geophagy may serve as a coping mechanism, a more effective management strategy would be to reduce or eliminate the provisioning of human foods. The potential risks associated with soil consumption, particularly from pollutants near busy roads, further complicate the issue.

The Guardian

Dr. Lemoine emphasized the need for further research to understand the exact effects of soil on the macaques' digestive systems, noting that "soils, particularly those rich in clay, are known to alleviate gut pH (acidity) and modify microbiome composition." He also pointed out that while soil consumption may help the macaques feel better during digestion, it does not directly aid in digesting junk food.

Monkeys learn to self-medicate with soil to help them digest junk food

• “We think that eating this junk food disrupts the composition of the microbiome and we know that bacteria and minerals in soil can help recompose the microbiome and alleviate the negative effects,” — Dr. Sylvain Lemoine, University of Cambridge

The Guardian

• “The emergence of this behaviour in macaques is both a functional and cultural one, like nutcracking in chimps, except it is driven entirely by proximity to humans” — Dr. Sylvain Lemoine, University of Cambridge

Monkeys learn to self-medicate with soil to help them digest junk food

• “However, while geophagy may serve as a coping mechanism, a more effective management approach is to reduce or eliminate the provisioning of human foods,” she said.” — Dr. Paula Pebsworth, University of Texas at San Antonio

The Guardian

The adaptation of Gibraltar's macaques to their tourist-driven diet through soil consumption illustrates a remarkable example of behavioral flexibility in response to environmental changes. However, the implications of this behavior raise concerns about the long-term health of the macaques and the need for responsible tourist practices to protect their well-being.

Reuters